1. Field of the Invention
The invention provides a dish antenna rotation apparatus. The apparatus comprises a dish bracket and an elevation bracket. The dish bracket can more easily and exactly adjust a rotation angle. The elevation bracket can more easily and exactly adjust an elevation angle.
2. Description of the Related Art
A synchronous direct broadcast satellite (DBS) is a one point to multi-points communication system in which signals from the DBS can be received by a small antenna and a tuner device. Generally speaking, the DBS can receive signals from a specific earth surface transmitter, and then the DBS can send the signals to multiple earth surface receivers. After an earth surface receiver collects the signals of the DBS into a dish reflector, the signals are focused on at least one low noise block with feed convertor (LNBF), which is in the rear of the dish reflector. The LNBF can selectively receive the signal. The LNBF has the same functions as those for a filter and an amplifier, and further comprises a forward waveguide antenna and a backward component. The forward waveguide antenna can receive the signals, and the backward component can transform the radio frequency signals into the intermediate frequency signals to the tuner devices.
For the better communications between a receiver and a DBS, the receiver needs to be positioned based on the difference of longitudes and latitudes of the receiver and the DBS. In other words, the receiving angles of the receiver, such as a rotation angle, an elevation angle and an azimuth angle, have to be adjusted based on the location of the DBS.
According to the foregoing, a multi-beam antenna rotation apparatus can be used for receiving the signals of multiple satellites. The rotation apparatus can be adjusted to a selected rotation angle, to a selected elevation angle and to an azimuth angle of a dish antenna. Taking the U.S. and the PRC, for example, three DBSs are respectively located at 101 degrees west longitude, 110 degrees west longitude, and 119 degrees west longitude. Thus, the rotation angle of the apparatus ranges between +55 degrees and −55 degrees, and the elevation angle ranges between 0 degree and 65 degrees.
In addition, because the receiver is sensitive to the position of the DBSs and has to be able to endure 60 m/s of wind pressure, the receiver is more difficult to manufacture. Therefore, the design of a rotation apparatus of the receiver becomes very important.
FIG. 1 illustrates a present rotation apparatus for a dish antenna. The apparatus comprises a dish 10, an elevation bracket 20, a clamp 31, a mast 32 and a pedestal 33. The dish 10 includes two sides. One side is concave. The other side forms a flange 11. The flange 11 includes a pair of bolts 12 and a concentric axle 13. The elevation bracket 20 further comprises a pair of fold wings 22 and a bolt 23. The bolt 23 passes through the fold wings 22. Each of the fold wings 22 further comprises a first wing 221 and an adjacent second wing 222. Each first wing 221 is perpendicular to the respective adjacent second wing 222. Each first wing 221 further comprises a respective vertical groove 24, and each second wing 222 further comprises a respective horizontal groove 21. At least one of the second wings 222 further comprises an extending arm 223. The extending arm 223 comprises a concentric axle hole 25. The concentric axle hole 25 is coupled to the concentric axle 13 of the dish 10 in order to rotate the dish 10. After the dish 10 is rotated, the horizontal grooves 21 are coupled to the pair of bolts 12 to securely combine the dish 10 with the elevation bracket 20.
As shown in FIG. 1, a clamp 31 is attached to one of the fold wings 22. The bolt 23 passes through holes 36 in the fold wings 22 and through holes 37 in the clamp 31. The bolt 23 operates as a pivot to permit the clamp 31 to move with respect to the fold wings 22. The clamp 31 can rotate about the pivot 23  to a specific elevation angle. Then the clamp 31 is fixed in the vertical grooves 24 of the fold wings 22. The clamp 31 is further attached to the mast 32. The mast 32 further couples to the pedestal 33. The pedestal 33 supports the dish 10.
As shown in FIG. 1, the elevation bracket 20 comprises the two separating fold wings 22. The fold wings 22 are fixed to the pair of bolts 12 of the flange 11 of the dish 10 by only two screws. For the rotation apparatus of FIG. 1, the receivers have to be adjusted in accordance with the position of a selected one of the DBSs, and the receivers have to be able to endure 60 m/s of wind pressure. Also, because the fold wings 22 of the elevation bracket 20 include both the vertical grooves 24 and the horizontal grooves 21, the vertical grooves 24 and horizontal grooves 21 cannot be independently adjusted. In other words, once the position of one of the grooves is changed, the positions of the other grooves also have to be readjusted.
Furthermore, the fold wings 22 are coupled to each other by only the bolt 23. This causes the symmetry of the fold wings to be weak. Thus, the fold wings cannot be symmetrically rotated with the dish 10, which results in a poor receiving precision. Furthermore, once the fold wings 22 are respectively readjusted, the fold wings 22 may change shape due to forced pulling and forced dragging. The changed shapes of the fold wings may further result in rough rotating when the next adjustment is made, which makes it more difficult to adjust the position of the clamp 31 for an accurate elevation angle.